Only single carrier working mode is specified in a current 3rd generation TDD communication mode specification (refer to relating technology specifications in 3GPP). FIG. 1 shows a single carrier cell channel allocation in a TD-SCDMA system specified in 3GPP standard. As shown in FIG. 1, taking a TD-SCDMA system with 3 carriers (f0, f1, f2) as an example, an independent cell may be constituted by one carrier. In each carrier, a broadcasting channel (BCH) and a paging channel (PCH) are arranged in its TS0 timeslot, an uplink physical random access channel (PRACH) is arranged in its TS1 or other uplink timeslots, a common control channel such as a fast physical access channel (FPACH) is arranged in its TS6 or any other downlink timeslots, and remaining code channels of the arranged timeslots and all code channels of remaining timeslots are used as uplink and downlink traffic channels. From a network view, each carrier corresponds to a cell and respective carrier in each cell works independently.
In order to meet a communication requirement in a high density application environment, base station is designed to work with multi-carriers. In a multi-carrier TDD mobile communication system designed based on this idea, a wireless base station adopting a multi-carrier working mode may use multi-carriers in one cell. For example, three carrier frequencies (f0, f1 and f2) are used in one cell to increase the cell capacity, in other words, such arrangements also reduce system cost, simplify system design, make control and management of the system easier and improve system efficiency. Based on the standard of the above 3rd generation mobile communication TDD communication mode, when the base station is designed to work with multi-carriers, each carrier may be processed only by regarding it as a single cell. Therefore, in a same geographical position, there might be multiple independent cells under the same or similar coverage conditions provided. For example, one mobile communication system operator in many European countries can obtain 5 Mhz TDD frequency band and if the TD-SCDMA system is adopted, it can support 3 carriers, i.e., three cells will be covered in the same geographical position.
Taking a case using TD-SCDMA system as an example, a system resource (channel) allocation status in each cell (each carrier) in the system can be obtained from FIG. 1. When a cellular mobile network is to be organized and it covers large areas, this system resource (channel) allocation technology has following disadvantages:
(1) Low system efficiency. Since each carrier must be configured with common channels, each carrier's channel resource for uplink and downlink traffic is reduced greatly. For example, TS0 of each carrier has been allocated to BCH and PCH; in a downlink timeslot, such as TS6, 8 code channels must be allocated to FPACH; in a uplink timeslot, such as TS1, 2 code channels must be allocated to PRACH. Thus when spreading factor is 16, only 86 (14+8+4×16) code channels can be allocated to uplink and downlink traffic by each carrier, in another word, only 21 bidirectional voice service or a unidirectional 384 kbps data service can be supported.
(2) Complicated management and control leading to efficiency decrease of some functions. The system considers that the same base station in the same geographical position covers three cells, which makes the number of cells increases, and increases the management and control complexity. For an important function of dynamic channel allocation (DCA) in the mobile communication system, since the execution of this function can only occupy the resources of the local cell while the resources of the local cell is very limited (spreading factor is 16 and available timeslots and code channels are limited, i.e., available overall resources which can be allocated are limited), the DCA technology can not put to effect because of the limited resources.
(3) It will be hard for the system to process a random access or a handover of a terminal, which causes detection difficulty. In the cellular mobile communication system, the terminal may move to a position near 3 to 6 base stations. FIG. 2 shows a typical cellular mobile network which illustrates base stations 101, 102 . . . 108 (represented by triangles respectively) and the position of terminal 500 (represented by a diamond), wherein the nearest base stations are 103, 105 and 107 and the near base stations are 101, 102, 103, 104, 106, 108 and the terminal 500 receives signals 201, 202 . . . 208 from the base stations 101, 102 . . . 108 respectively and interference signals 301 and 302 from distant co-frequency base stations. The terminal 500 may receive different downlink pilot codes from neighboring cells on a downlink pilot timeslot (DwPTS) of each carrier, wherein the number of the downlink pilot codes equals to a product of the number of the base stations and the number of carriers of each base station. For example, if an occupied bandwidth is 10 MHz and each base station may use 6 carriers, the terminal 500 may receive signals from around or more than 20 cells. At this time, since it is impossible for the downlink pilot signals from different cells to be synchronous, SNR can reach −5 to −8 dB on each carrier frequency, which makes it more difficult for the terminal to search for and to access the cell; while in a connected mode (communication mode), if each base station uses multi-carriers, the terminal may detect signals from around 10 different cells and levels of these signals are close, which causes detection difficulty. The above cases thus lead to many wrong handovers and handover difficulty, which causes the system unstable.
(4) In the cellular network, after being transmitted for a far distance, the downlink pilot signals (transmitted in DwPTS), such as 301 and 302 shown in FIG. 2, of distant co-carrier frequency base stations may interfere uplink pilot signals transmitted by the terminal 500, which increases the difficulty of accessing the system.
Generally, the wireless base stations in the cellular mobile communication system adopt multi-carrier working mode to increase the cell capacity, in other words, the system capacity is increased while the system cost is reduced. For the TD-SCDMA system (as one of the 3rd generation mobile communication system standards), the current standard only supports single carrier working mode and when adopting the multi-carrier working mode, each carrier may be processed only by regarding it as a single cell, which thus causes the above four disadvantages. Therefore, it is necessary to design radio resource (channel) allocating method for a multi-carrier TDD mobile communication system realizing multi-carrier working mode in a cell or a sector, so as to support the multi-carrier working mode for the multi-carrier TDD mobile communication system.